This invention relates generally to mobile or cellular telephone systems and, more particularly, to mobile telephones that operate under the standard known as Global Systems for Mobile Communications (GSM). There is a well recognized need to identify the location of cellular telephone users, to provide emergency services such as police, medical assistance, fire response and rescue, and also to help the operator of the system to provide improved cellular communications. The Global Positioning System (GPS) permits users of GPS receivers to determine their respective positions to a high degree of accuracy. GPS receivers are used for a variety of applications, including navigation anywhere on or near the earth, and precision survey work. GPS data can be provided in conventional latitude and longitude form, or in terms of street addresses. It will be appreciated from the foregoing that there are many situations in which it would be desirable to have GPS location data pertaining to a mobile telephone user made available to system operators, and perhaps to a user designated to receive voice data from the sending user telephone. The present invention addresses this need, as will become apparent from the following summary and detailed description.
The present invention resides in a novel method, and corresponding apparatus for its use, for embedding GPS location data pertaining to a GSM cellular telephone in successive samples of voice data transmitted by the GSM cellular telephone. The GPS data are obtained from a GPS receiver integrated into the GSM cellular telephone, to provide telephone location data to a receiver of the voice data.
Briefly, and in general terms, the method of the invention includes the steps of obtaining position data using a Global Positioning System (GPS) receiver integrated into a GSM cellular telephone; storing the position data in a buffer; processing samples of voice data for transmission from the GSM cellular telephone; embedding position data in successive samples of voice data; transmitting the successive samples of voice data, including the embedded position data; receiving successive samples of voice data and embedded position data at a cellular telephone receiver; and recovering the embedded position data from the successive samples of voice data.
More specifically, the step of obtaining position data includes editing and formatting the position data to contain a fixed number of bits of data each second. Further, the fixed number of bits represents position data for three orthogonal directions, velocity data for the same three directions, and a figure of merit indicative of reliability of the data. In the illustrative embodiment of the invention, the fixed number of bits per second are formatted as nineteen 16-bit words, including nine words of position data, nine words of velocity data and one word containing the figure of merit.
The invention may also be defined as a cellular telephone using Global Systems for Mobile Communication (GSM) protocols, the telephone comprising a voice sampling module; a GSM voice compression module utilizing a Regular Pulse Excitation/Long-Term Predictor (RPE/LTP); a Global Positioning System (GPS) receiver integrated into the telephone, for generating GPS position data; a GPS data editor, for reformatting the GPS data; a GPS data buffer for temporally storing GPS data until voice samples become available; a GPS data injection module, for encoding GPS data into successive samples of voice data, by replacing selected bits of voice data with GPS data; a transmitter, for transmitting the successive samples of voice data; a receiver, for receiving voice data transmitted from another cellular telephone; and a GPS data recovery module, for recovering embedded position and velocity data from successive voice samples received.
It will be appreciated from the foregoing that the, present invention provides a useful technique for combining GPS location data with voice signals in a GSM format. Other aspects and advantages of the invention will become apparent from the following more detailed description, taken in conjunction with the drawings that are briefly described below.